MDS PREP
What is the typical setting expansion of a high expansion dental stone?
1) Less than 0.1%.
2) 0.1-0.2%.
3) 0.2-0.3%.
4) More than 0.3%.
High expansion dental stones are designed to expand more than typical dental stones to compensate for the contraction of other materials and ensure a precise fit for restorations.
What is the main advantage of using Ormocers in dental restorations?
1) They have a high coefficient of thermal expansion.
2) They have excellent biocompatibility and resistance to masticatory loading.
3) They are easy to manipulate and require minimal finishing.
4) They can be used in high-stress bearing areas without reinforcement.
The main advantage of using Ormocers is their excellent biocompatibility and resistance to masticatory loading. They also have good esthetic properties, resembling those of natural teeth.
What are the two primary components of the liquid phase of a denture base resin?
1) Nonpolymerized methyl methacrylate and a cross-linking agent
2) Prepolymerized beads and benzoyl peroxide
3) Hydroquinone and glycol dimethacrylate
4) Monomer and initiator
The liquid phase of a denture base resin primarily consists of nonpolymerized methyl methacrylate (monomer) and a cross-linking agent like glycol dimethacrylate.
What is the primary function of a light-curing unit in the polymerization of resin-based materials?
1) To generate heat for setting.
2) To activate the photosensitizer and initiate the polymerization reaction.
3) To accelerate the chemical reaction.
4) To increase the viscosity of the material.
Light-curing units emit light at specific wavelengths that are absorbed by the photosensitizer in the resin, triggering the free radical polymerization process and setting the material.
What is the effect of increasing the concentration of the amine initiator in a light-cured composite?
1) It decreases the depth of cure.
2) It increases the depth of cure.
3) It has no effect on the depth of cure.
4) It can lead to premature polymerization.
An excessive amount of amine initiator can lead to a faster reaction rate and a decrease in the depth of cure, as the light may not be able to penetrate deep enough into the material to activate the entire polymerization process.
What is the primary difference in polymerization between heat-activated and chemically activated resins?
1) Heat-activated resins have a lower degree of polymerization
2) Chemically activated resins have a higher degree of polymerization
3) There is no difference in the degree of polymerization
4) The polymerization process is the same for both types of resins
Heat-activated resins typically have a higher degree of polymerization, resulting in less residual monomer and greater strength compared to chemically activated resins.
Bonding of GIC to tooth structure is brought about by
1) metal ions
2) hydroxyl bond
3) carboxyl bond
4) ionic bond
Dental Materials Answer: 3
one ot the main adanhtges of GIC as a restoratie material was its ability to form chemical bonds with the tooth structure.
Bonding in GIC primarily invokes chelation of carboxyl groups of the polyacids sith the calcium in the apatite of enamel and dentin. Bond rength of enamel is always greater than that of dentin due to higher mineral content. The bonding is improved by the removal of the debris layer called smear layer’ by a process called conditioning.
Polyethers are susceptible to dimensional change if immersed for a long time. The recommended maximum time to immerse in disinfectant is
1) 1 minute
2) 10 minutes
3) 30 minutes
4) 1 hour
Dental Materials Answer: 2
The polyethers are susceptible to dimensional change if immersed for a long time (>10 min) because of their pronounced hydrophilic nature.